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  <title>Execute an external program and display raw output</title>

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</div><hr /><div id="function.passthru" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">passthru</h1>
  <p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">passthru</span> &mdash; <span class="dc-title">Execute an external program and display raw output</span></p>

 </div>

 <div class="refsect1 description" id="refsect1-function.passthru-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="type"><span class="type void">void</span></span> <span class="methodname"><strong>passthru</strong></span>
    ( <span class="methodparam"><span class="type">string</span> <code class="parameter">$command</code></span>
   [, <span class="methodparam"><span class="type">int</span> <code class="parameter reference">&$return_var</code></span>
  ] )</div>

  <p class="para rdfs-comment">
   The <span class="function"><strong>passthru()</strong></span> function is similar to the
   <span class="function"><a href="function.exec.html" class="function">exec()</a></span> function in that it executes a
   <em><code class="parameter">command</code></em>. This function
   should be used in place of <span class="function"><a href="function.exec.html" class="function">exec()</a></span> or
   <span class="function"><a href="function.system.html" class="function">system()</a></span> when the output from the Unix command
   is binary data which needs to be passed directly back to the
   browser.  A common use for this is to execute something like the
   pbmplus utilities that can output an image stream directly.  By
   setting the Content-type to <em>image/gif</em> and
   then calling a pbmplus program to output a gif, you can create
   PHP scripts that output images directly.
  </p>
 </div>


 <div class="refsect1 parameters" id="refsect1-function.passthru-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<em><code class="parameter">command</code></em></dt>

     <dd>

      <p class="para">
       The command that will be executed.
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">return_var</code></em></dt>

     <dd>

      <p class="para">
       If the <em><code class="parameter">return_var</code></em> argument is present, the 
       return status of the Unix command will be placed here.
      </p>
     </dd>

    
   </dl>

  </p>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-function.passthru-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   没有返回值。
  </p>
 </div>


 <div class="refsect1 notes" id="refsect1-function.passthru-notes">
  <h3 class="title">注释</h3>
  <div class="warning"><strong class="warning">Warning</strong><p class="para">当用户提供的数据传入此函数，使用
<span class="function"><a href="function.escapeshellarg.html" class="function">escapeshellarg()</a></span> 或 <span class="function"><a href="function.escapeshellcmd.html" class="function">escapeshellcmd()</a></span>
来确保用户欺骗系统从而执行任意命令。</p></div>
  <blockquote class="note"><p><strong class="note">Note</strong>: <p class="para">如何程序使用此函数启动，为了能保持在后台运行，此程序必须将输出重定向到文件或其它输出流。否则会导致
PHP 挂起，直至程序执行结束。</p></p></blockquote>
  <blockquote class="note"><p><strong class="note">Note</strong>: <span class="simpara"><a href="features.safe-mode.html" class="link">安全模式</a> 启用时，可仅可用
<a href="ini.sect.safe-mode.html#ini.safe-mode-exec-dir" class="link">safe_mode_exec_dir</a> 执行文件。实际上，现在不允许在到可执行的路径中存在 <em>..</em> 组件。</span></p></blockquote>
  <div class="warning"><strong class="warning">Warning</strong><p class="simpara"><a href="features.safe-mode.html" class="link">安全模式</a> 启用时，命令字符串会被
<span class="function"><a href="function.escapeshellcmd.html" class="function">escapeshellcmd()</a></span> 转换。因此，<em>echo y | echo x</em> 会变成
<em>echo y \| echo x</em>。</p></div>
 </div>


 <div class="refsect1 seealso" id="refsect1-function.passthru-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="function.exec.html" class="function" rel="rdfs-seeAlso">exec()</a> - Execute an external program</span></li>
    <li class="member"><span class="function"><a href="function.system.html" class="function" rel="rdfs-seeAlso">system()</a> - Execute an external program and display the output</span></li>
    <li class="member"><span class="function"><a href="function.popen.html" class="function" rel="rdfs-seeAlso">popen()</a> - 打开进程文件指针</span></li>
    <li class="member"><span class="function"><a href="function.escapeshellcmd.html" class="function" rel="rdfs-seeAlso">escapeshellcmd()</a> - Escape shell metacharacters</span></li>
    <li class="member"><a href="language.operators.execution.html" class="link">backtick operator</a></li>
   </ul>
  </p>
 </div>

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